BUG: quiverkey must set the vector figure attribute
ENH : improve error invalid error message for subplot

Closes #2098

If user passes in a not-three-digit integer, raise `ValueError`
instead of letting the error propagate up from much farther down
the stack
Merge pull request #2782 from efiring/quiverkey_set_figure

BUG: quiverkey must set the vector figure attribute
Merge pull request #2780 from tacaswell/subplot_errormsg

ENH : improve error invalid error message for subplot
missing mask for scroll event
Merge pull request #2793 from fariza/scroll_event_gtk3

missing mask for scroll event
fix typo in documentation

beyone -> beyond
Merge pull request #2794 from daydreamt/master

fix typo in documentation